The Bush administration routinely accuses the Tehran regime of arming and funding some of the Shiite militias taking on American troops.

Now the US has taken the rhetoric one step further.

General David Petraeus claims Iran's Ambassador to Iraq, Hassan Kazemi-Qomi, belongs to the secretive Quds force. This is an elite unit of Iran's revolutionary guard - a force believed to be behind not just some of the violence in Iraq, but also propping up groups like Hamas and Hezbollah.

General Petraeus took aim at the ambassador while touring a US military base near the Iranian border.

"The Quds force controls the policy for Iraq. There should be no confusion about that either," he said.

"The ambassador's a Quds force member. Now he has diplomatic immunity and therefore he is obviously not subject, and he is acting as a diplomat."

Iran has not commented on the allegation, but it has taken issue with the US military's assertions that it has captured a number Quds force members in Iraq.

A Foreign Ministry spokesman says Iran wants the Americans to announce the names of the captured militia's that they say are members of the Quds force.

But General Petraeus has scoffed at the comment.

"There is no debate that the individuals who we have detained are Quds force members, and the individual detained in northern Iraq," he said.

"Let's be very clear about this. We have absolute assurance of who he is, what he has done in the past, what he has provided in terms of accelerants, what his position is in the Quds force.

"Again, these are not in question."

Also not in question, according to some military analysts, is the Bush administrations desire to go after the Tehran regime.

Statements like those by General Petraeus could be part of an attempt to turn US public opinion in favour of military action against Iran - in particular, air strikes against revolutionary guard bases.

From the President down, the official line is that negotiation, not confrontation is the way forward. But it is clear the verbal barrage against Iran is becoming much more intense.

Where this will lead, nobody yet knows.

But, for its part, the Iraqi Government believes Iran is not the maligned presence the US is making it out to be.

Iraq's President, Jalal Talabani, insists Iran has been helpful in taming some of the more volatile Shiite groups in his country.